Field of the Invention
The aspect of the embodiments relates to a display control apparatus and a method for controlling the display control apparatus, and, in particular, to control of luminance of a display apparatus.
Description of the Related Art
Conventionally, there have been known video systems configured to image an object by an imaging apparatus and display this video image on a display apparatus to enable a user to view the video image. In such a kind of video system, when imaging the object, the imaging apparatus converts a tone of the object into a video signal by converting luminance of the object into a code value based on a gamma characteristic of the imaging apparatus. Then, when displaying the video image, the display apparatus converts the code value provided as the video signal into an output luminance value based on a gamma characteristic of the display apparatus. By the processing performed in this manner, the video system can cut out a range covering limited brightness from the real-world object that has an extremely wide dynamic range, and display the video image while making it fall within a limited narrow dynamic range of the display apparatus. Generally, a measure for extending an input dynamic range with use of knee correction processing is employed to secure a practical input dynamic range at the imaging apparatus when the object is imaged (Japanese Patent Application Laid-Open No. 2002-223373).
Generally, the imaging apparatus is configured to secure the practical input dynamic range by compressing a contrast in a region which is from intermediate luminance to high luminance. However, in such a case, a gradation characteristic as a system total, which is a total of the gamma characteristic of the imaging apparatus and the gamma characteristic of the display apparatus, ends up becoming an unnatural gradation characteristic in which the contrast is compressed at a high-luminance portion compared to a low-luminance portion. One possible solution to avoid such a disadvantage is that the gradation characteristic as the system total, which is the total of the gamma characteristic of the imaging apparatus and the gamma characteristic of the display apparatus, is linearized with respect to the luminance. Linearizing the gradation characteristic with respect to the luminance allows an entire region from a dark portion to a highlight portion to be expressed with a more natural gradation. However, when the video image having the gradation characteristic linearized with respect to the luminance is displayed on the display apparatus, the intermediate luminance and the low luminance are darkened although the natural gradation can be attained, compared to the generally used gradation characteristic that is not the gradation characteristic linearized with respect to the luminance.
Further, monitors built in reproduction apparatuses are configured to allow luminance thereof to be controlled according to the video image to be reproduced, but, regarding monitors connected to external video output terminals, such as High-Definition Multimedia Interface (HDMI) (registered trademark), the luminance cannot be controlled from the reproduction apparatus side on many of them. Therefore, there is such a situation that, when the video image captured so as to achieve the gradation characteristic linearized with respect to the luminance is output to such an external monitor and the video image is displayed with a normal luminance setting, the displayed video image is unintentionally darkened.